What’s Vulnerable › Vulnerabilities

CVE-2026-2739: bn.js affected by an infinite loop

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-20 · updated 2026-06-17
• Weakness: CWE-835

Description

This affects versions of the package bn.js before 5.2.3. Calling maskn(0) on any BN instance corrupts the internal state, causing toString(), divmod(), and other methods to enter an infinite loop, hanging the process indefinitely.

Affected products

• Npm Bn.Js: before 4.12.3; from 5.0.0 before 5.2.3 — fixed in 4.12.3, 5.2.3
• bn.js: before 5.2.3 — fixed in 5.2.3

How to fix

Upgrade to a fixed version: Npm Bn.Js 4.12.3, 5.2.3; bn.js 5.2.3. Check the vendor advisory for mitigations.

References

• https://gist.github.com/Kr0emer/02370d18328c28b5dd7f9ac880d22a91
• https://github.com/indutny/bn.js/commit/33df26b5771e824f303a79ec6407409376baa64b
• https://github.com/indutny/bn.js/issues/186
• https://github.com/indutny/bn.js/issues/316
• https://github.com/indutny/bn.js/pull/317
• https://security.snyk.io/vuln/SNYK-JS-BNJS-15274301

Get alerted when CVE-2026-2739 or the next vulnerability affects your stack